Messages in this thread | | | Date | Wed, 2 Mar 2022 12:55:06 -0800 | Subject | Re: [PATCH bpf-next v1 1/9] bpf: Add mkdir, rmdir, unlink syscalls for prog_bpf_syscall | From | Yonghong Song <> |
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On 2/25/22 3:43 PM, Hao Luo wrote: > This patch allows bpf_syscall prog to perform some basic filesystem > operations: create, remove directories and unlink files. Three bpf > helpers are added for this purpose. When combined with the following > patches that allow pinning and getting bpf objects from bpf prog, > this feature can be used to create directory hierarchy in bpffs that > help manage bpf objects purely using bpf progs. > > The added helpers subject to the same permission checks as their syscall > version. For example, one can not write to a read-only file system; > The identity of the current process is checked to see whether it has > sufficient permission to perform the operations. > > Only directories and files in bpffs can be created or removed by these > helpers. But it won't be too hard to allow these helpers to operate > on files in other filesystems, if we want. > > Signed-off-by: Hao Luo <haoluo@google.com> > --- > include/linux/bpf.h | 1 + > include/uapi/linux/bpf.h | 26 +++++ > kernel/bpf/inode.c | 9 +- > kernel/bpf/syscall.c | 177 +++++++++++++++++++++++++++++++++ > tools/include/uapi/linux/bpf.h | 26 +++++ > 5 files changed, 236 insertions(+), 3 deletions(-) > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > index f19abc59b6cd..fce5e26179f5 100644 > --- a/include/linux/bpf.h > +++ b/include/linux/bpf.h > @@ -1584,6 +1584,7 @@ int bpf_link_new_fd(struct bpf_link *link); > struct file *bpf_link_new_file(struct bpf_link *link, int *reserved_fd); > struct bpf_link *bpf_link_get_from_fd(u32 ufd); > > +bool bpf_path_is_bpf_dir(const struct path *path); > int bpf_obj_pin_user(u32 ufd, const char __user *pathname); > int bpf_obj_get_user(const char __user *pathname, int flags); > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > index afe3d0d7f5f2..a5dbc794403d 100644 > --- a/include/uapi/linux/bpf.h > +++ b/include/uapi/linux/bpf.h > @@ -5086,6 +5086,29 @@ union bpf_attr { > * Return > * 0 on success, or a negative error in case of failure. On error > * *dst* buffer is zeroed out. > + * > + * long bpf_mkdir(const char *pathname, int pathname_sz, u32 mode)
Can we make pathname_sz to be u32 instead of int? pathname_sz should never be negative any way.
Also, I think it is a good idea to add 'u64 flags' parameter for all three helpers, so we have room in the future to tune for new use cases.
> + * Description > + * Attempts to create a directory name *pathname*. The argument > + * *pathname_sz* specifies the length of the string *pathname*. > + * The argument *mode* specifies the mode for the new directory. It > + * is modified by the process's umask. It has the same semantic as > + * the syscall mkdir(2). > + * Return > + * 0 on success, or a negative error in case of failure. > + * > + * long bpf_rmdir(const char *pathname, int pathname_sz) > + * Description > + * Deletes a directory, which must be empty. > + * Return > + * 0 on sucess, or a negative error in case of failure. > + * > + * long bpf_unlink(const char *pathname, int pathname_sz) > + * Description > + * Deletes a name and possibly the file it refers to. It has the > + * same semantic as the syscall unlink(2). > + * Return > + * 0 on success, or a negative error in case of failure. > */ > #define __BPF_FUNC_MAPPER(FN) \ > FN(unspec), \ > @@ -5280,6 +5303,9 @@ union bpf_attr { > FN(xdp_load_bytes), \ > FN(xdp_store_bytes), \ > FN(copy_from_user_task), \ > + FN(mkdir), \ > + FN(rmdir), \ > + FN(unlink), \ > /* */ > > /* integer value in 'imm' field of BPF_CALL instruction selects which helper [...]
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